A device for the abatement of noxious emission from heating plants

ABSTRACT

The present invention refers to a device and a related method for the abatement of the noxious emissions into atmosphere coming from domestic heating plants, such as pellet stoves, fuel oil stoves and wood-burning stoves, or gas boilers, and of the emissions from wood-burning ovens for domestic and commercial use, and of the emissions from industrial plants and from large ships.

FIELD OF THE INVENTION

The present invention refers to a device and a related method for theabatement of the noxious emissions into atmosphere from the domesticheating plants, such as pellet stoves, fuel oil stoves and wood-burningstoves, or gas boilers, as well as of the emissions from wood-burningovens for domestic and commercial use, and of the emissions fromindustrial plants and from large ships, and it finds thereforeapplication in the field of such plants.

STATE OF THE ART

The whole world is currently experiencing a period of profoundenvironmental crisis mainly due to the needs that modern life imposes onus, to the increased consumption and consequent industrial production,to the thoughtless use of heating means and to the increase of vehiculartraffic. Also under the pressure of public opinion and of theassociations newly formed in recent years for the protection ofenvironment, there is now a plethora of initiatives from internationalorganizations to local governments aimed at limiting the damages causedby pollution and especially at reducing their causes for the future.Unfortunately, these initiatives usually result in mild remedies such asalternating use of motor vehicles, having purely palliative and apparenteffects, while cities continue to be plagued by serious air pollutionproblems with more than harmful consequences on people's health.

Domestic heating means as well as heating plants for tertiary and tradesectors represent a significant source of pollution, comparable to thetransport sector or the industrial production as far as harmfulemissions are concerned. If up to now, at least in the transport sector,national and European Community regulations have been imposedestablishing limits to atmospheric emissions through the Euroclassification of vehicles, for the domestic emissions no significantenvironmental measures have been adopted. This may be due to the lack ofinformation on this type of emissions, to the difficulty to register thenumber of stoves and boilers on a certain territory; it is also notknown the actual impact on environment of emissions of pollutants suchas those from domestic fuel oil boilers or from wood stoves, thereforeup to now specific, effective measures have not been adopted. Inaddition to this, there are economic reasons but also psychologicalreasons that guide the choice of a heating system rather than another:it is in fact proved that the emissions of particulate into theatmosphere from a fireplace or from a pellet stove or a wood stove aremuch greater than those emitted by a gas or natural gas boiler, evenhigher than emissions from fuel oil heating plants, but in general inrecent years wood or pellet heating plants have found enthusiasticsupporters, and this kind of heating plants has experienced a certainexpansion. In addition, the wood or pellet heating is considered a cheaptype of heating and the choice of a heating plant instead of another isjust driven by economic reasons, so that often these heating systems arewithout filters or special rooms of combustion, which are available inorder to generate lower quantities of particulate but they are discardedas more expensive. The result is that a fireplace or a pellet stove emitinto the atmosphere much higher particulate emissions than it is usuallyperceived; it has been estimated, for instance, that a single pelletstove emits in the atmosphere a quantity of particulate comparable tothat produced by 350 natural gas boilers.

Particulate matter or PM is among all pollutants in emissions fromplants, the one considered to have a greater negative effect on airquality, particularly in the cities where it is also produced by carexhausts. This term particulate matters usually indicates thesubstances, liquid and solid, suspended in the air and made of metals,silica, carbon particles, etc. having a diameter varying between a fewnanometres up to 500 micrometres and beyond. Particularly dangerous topeople's health is the particulate fraction known as PM10, consisting ofparticles of diameter less than 10 micrometres that, because of suchsmall size, once inhaled by people, may arrive in the deep airwaysdepending on their size, and even reach the alveolar walls of the lungs,with more or less harmful effects on the respiratory and cardiovascularsystems, up to determine the onset of tumours and other seriousdiseases.

In addition to the particulate emissions, the combustion of biomasses,and in particular of wood, produces organic compounds and nitrogenoxides in large amounts, thus irritating and harmful emissions for thehealth, and also contributes to the increase in the amount of CO₂ in theatmosphere, today no longer balanced by the forests. This gaseousemission is the greenhouse gas that is most responsible for globalwarming and for depletion of the ozone layer surrounding the earth, soit is a dangerous environmental pollutant to all effects.

Even the exhaust gases from large ships are considered a major source ofair pollution in the commercial and tourist harbours; since they containnearly 10% sulphur, these exhaust gases also contribute to acid rain,which damages crops and buildings.

CH 676436 discloses a process for the treatment of the gas exiting fromdomestic and industrial plants.

For the above said reasons it is strongly felt the issue of thepolluting emissions from the domestic or commercial plants, and inparticular the issue of the emissions of particulate materials and ofCO₂. To date however it is still unsolved the technical problem ofproviding a device efficient in reducing such emissions, without havingsecondary drawbacks or conferring restrictions to the plants.

SUMMARY OF THE INVENTION

Scope of the present invention is to provide a device for the abatementof noxious emissions from the outlet of the domestic heating plants andof the commercial wood-burning ovens, useful in particular for thereduction of particulate and of carbon dioxide in the emissions, havinga high efficacy of abatement thus contributing to the reduction of theair pollution caused by this kind of plants.

A further scope of the invention is to provide a device of the abovesaid type that may be easily installed in the flue of any kinds ofplants without impairing their efficiency or causing other drawbacks inthe operations of the plant itself.

Still a further scope of the invention is to provide a device of theaforesaid type that is able to accumulate the noxious emissions in theinside and can be easily regenerated maintaining over time a highefficiency of emissions abatement.

Still a further scope of the present invention is to provide anefficacious method for the abatement of the noxious emissions from thedomestic heating plants and from the wood-burning ovens for commercialuse, comprising treating the gases coming from the plants before theiremission in the atmosphere.

Still a further scope of the present invention is to provide a deviceand a method efficacious for the abatement of the noxious emissions fromindustrial plants and from large ships, comprising treating theirexhaust gas before entry into the atmosphere.

These scopes are achieved by the device and the method according to thepresent invention, whose essential characteristics are respectivelydefined in the independent claims here attached.

Further important features are included in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the device of the invention will beevident from the following exemplary, non-limiting description ofembodiments thereof, with reference to the attached drawings wherein:

FIG. 1 shows a front view, partially exploded, of the present device ina first embodiment thereof;

FIG. 2 is a front view of the inner structure (part a) and of theelement external container (part b) of the device of FIG. 1;

FIG. 3 is a front view of the present device in a second embodimentthereof;

FIG. 4 shows a view in longitudinal section of an element of the innerstructure in the device of FIG. 1 or of FIG. 3, indicated in thefollowing as “micro-perforated element”.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the attached figures, a device of the invention fortreating the exhaust emissions from domestic heating plants and fromcommercial ovens comprises a tubular container 1 having substantiallycylindrical form, provided with at least two holes, one in the centralpart of the device for the inlet, through a special inlet duct E, ofexhaust gases to be treated and one in the upper part for the outlet ofthe exhaust gases treated, through a special outlet duct U.

With particular reference to the FIGS. 1 and 2 the modular structure ofthe container 1 is shown in a preferred embodiment thereof (see inparticular the FIG. 2, part b), formed by three separated portions 11,12 and 13; in general, the container 1 consists of at least twoseparated portions, joined to each other by supporting flanges betterdescribed in the following, so as to facilitate the maintenance of thedevice and possible operations of repair that the inner structure mayrequire.

A first embodiment of the present device, particularly suitable for thetreatment of emissions coming from stoves and boilers, is illustrated inFIG. 2a , wherein from the duct E the exhaust gas to be treated isdirected inside an array of perforated elements 3, having for instance asubstantially parallelepiped form and positioned in a radial pattern ona plane perpendicular to the longitudinal axis of the container 1, andplaced in a lower portion thereof, for instance at the portion 11 of thecontainer with reference to the FIG. 2b . The micro-perforated elements3 are positioned on an inner cylindrical surface 4 through which theyare in fluid communication with the inside of the device wherein theemissions to be treated arrive. Through the elements 3 and theirmicro-perforated surface the exhaust gas then comes out in theinterspace formed between the portion 11 of external container and theinner cylindrical surface 4. In this portion 11 of container anabsorbing solution is contained in such amount as to maintain the arrayof perforated elements 3 completely immersed in this solution, with thegas that escapes by bubbling inside the solution; therefore, in thepresent description, the array of elements 3 is sometimes referred to as“bubbler”. Advantageously, the level of absorbing solution exceeds forinstance the height of the array of elements 3 of 5-10 cm, so that theircomplete immersion in the solution is ensured.

In the present invention by “absorbing solution” any liquid substance orsolution is meant, which is suitable for the abatement of the noxioussubstances present in the exhaust gases, in particular of theparticulate matters and of the carbon dioxide; preferably by “absorbingsolution” a concentrated aqueous solution of ethylene glycol is meant,and more preferably an ethylene glycol aqueous solution 50%. Theseaqueous solutions of ethylene glycol have been widely used also in theautomotive industry, in particular as an anti-freezing liquid additivein combustion engines, in fuels and in the tanks for liquids to wash carglasses. As a matter of fact, ethylene glycol generates a cryoscopiclowering and an ebullioscopic raising of water, that respectively makethis solution solidify at −38° C. and boil at +108° C., therefore thesolution remains liquid in a very wide range of temperatures, to alsoinclude temperatures in the most extreme weather conditions, from whichderives the use as anti-freezing additive or as cooling liquid forradiators in combustion engines. The aqueous solution of ethylene glycolaccording to the invention can moreover comprise further agents usefulfor the abatement of the noxious substances in exhaust gases, forinstance one or more oxidising agents.

The structure of the present gas bubbler with reference to a particularembodiment thereof is illustrated in greater details in the FIG. 4 thatillustrates the structure of the single element 3. From the duct E thegaseous emissions to be treated go into the elements 3, from which theycome out through holes on their surface. According to a preferredembodiment of the present device, the elements 3 have the holespositioned on their only surface facing the interspace between thesurface 4 and the portion 11 of container; as a matter of fact, in thisway, the gas comes out from the gas bubbler maximising the residencetime of the gas bubbles in contact with the absorbing solution. This canbe appreciated in particular from the FIG. 4, wherein the numeral 31indicates the perforated surface of the element 3. Still with referenceto the FIG. 4, a particular embodiment is illustrated wherein theelement has such an inner structure that the gas entering the duct E,directly or by means of a collection container, through an inlet hole 33is directed towards the perforated surface 31 through a curved duct 32.

According to a preferred embodiment of the invention, the holes inelements 3 of the gas bubbler have moreover such dimensions that the gasflow exiting from them towards the solution is finely divided creatingmicro-bubbles, and typically these holes have a diameter comprisedbetween 0.7 and 5.0 mm, and preferably equal to about 3.5 mm. Thispreferred feature of the present device allows maximising the efficiencyin the treatment of the gas in the absorbing solution all otherconditions being the same, thanks to a wider contact surface between thegas bubbles and the solution itself; and moreover allows an easierascent of the gas bubbles inside the container facilitating theirescape.

The microbubbles of treated gas inside the absorbing solution thereforego upwards inside the container 1 towards a second array of perforatedelements 5, for instance of substantially parallelepiped form andpositioned in a radial pattern on a plane perpendicular to thelongitudinal axis of the container 1, and placed in an upper portionthereof, for instance of the portion 13 with reference to the FIG. 2,above the absorbing solution. The gas can go upwards inside thecontainer thanks to the holes on the supporting flanges for the portionsof the container 1; with reference to the FIG. 2a the holes are visibleon the flange 6, which joins the portions 11 and 12 of the container 1,and on the flange 7, which joins the portions 12 and 13 of the samecontainer. The gas coming from the holes on the flange 7 may enterthrough their micro-perforated surface inside the elements 5, in fluidcommunication with the inside of the cylindrical surface 8 on which theylean, and by them be directed towards the outlet duct U.

The second array of micro-perforated elements 5 is in fact incommunication with the outlet duct U of the treated exhaust gases,directly or through a collecting element, which puts in communicationthe elements 5 with the outlet duct U. As it is for the above-mentionedgas bubbler and the elements 3, also for the array of perforatedelements 5 an embodiment is preferred wherein the holes have the sizereported above for the elements 3 and/or they are positioned only on thesurface of the element 5 that faces the interspace between the surface 8and the portion 13 of the container.

According to a particular embodiment of the invention the present devicemay further comprise, in a portion of the container 1 intermediatebetween the two arrays of micro-perforated elements 3 and 5, a modulefor producing electric energy from the power of the exhaust gases flowexiting the device, for instance by means of hydroelectric turbinesconnected to an inverter.

Advantageously, the above said module for producing energy is aremovable module, which can be installed or uninstalled with relativeease depending on the needs in the use of the present device.

With particular reference to the FIG. 3 here attached a secondembodiment of the present device is described, particularly suitable forthe treatment of the emissions coming from commercial ovens andfireplaces, wherein from an inlet duct E on the bottom of the device theemissions to be treated are forced to pass through an absorbing solutionas described above, contained in a tubular portion of surface 4 on whichare positioned in a radial pattern micro-perforated elements 3, having aconfiguration and position as described above for the device of FIG. 2a. The treated gas at the outlet of the micro-perforated elements 3 goupwards inside the container 1 and, through the holes in a flange 7, getto the micro-perforated elements 5 positioned in a radial pattern on atubular surface 8 by entering through their micro-perforated surfaceinside the tubular 8 and from here the gas escapes from the outlet ductU. The internal structure of the present device illustrated in FIG. 3 isalso placed inside a container 1, preferably of modular structure, asthat illustrated in the FIG. 2b and described above.

The gas exiting from the duct U can be guided directly to the outsidefor emission into the air or, preferably, it is directed into adedicated tank outside of the container 1 containing a suitable filterfor capturing possible unburned particles escaped from the capture inthe gas bubbler, for instance an activated carbon filter.Advantageously, this tank can be opened for replacing this filter uponreaching saturation.

The present device may further comprise a system for the regeneration ofthe absorbing solution that has accumulated particulate matter comingfrom the treatment of the exhaust emissions. This system includes forinstance a tank 9, visible in the FIGS. 1, 2 and 3, for taking theabsorbing solution to be regenerated from the bottom of the container 1,containing a special filter suitable for the depuration of the solutionfrom the accumulated particulate and means for cooling the solution.Advantageously, also this filter can be easily replaced from the outsideupon reaching saturation. The so regenerated and cooled solution can bebrought back inside the container 1 by means of a recycling pump and aspecial pipeline. In this system one or more valves can be provided atthe aim of assisting and controlling the access at the filter of thesolution to be regenerated and the entry into the container 1 of theregenerated solution. According to a preferred embodiment of the presentdevice, this tank with filter is made of a transparent material so thata direct and immediate visual control of the exhaustion of the filter isallowed.

According to a preferred embodiment of the present device, the devicecan further comprise an additional tank provided in the inside with aspecial filter for collecting the condensate in order to collect theabsorbing solution dragged by the gas bubbles going upwards towards theoutlet. When present, this additional tank is preferably placed at anintermediate portion of the container 1, above the maximum level ofabsorbing solution, and it is provided by pipes 10 for transferring theliquid condensate back inside the container 1 so that it may be usedonce again for the treatment of emissions.

On the container 1, in a position more easily reachable from theoutside, an opening with a sealing plug may be provided for therefilling of the absorbing solution when this proves necessary.

The present device 1 further comprises, in the intermediate area betweenthe gas bubbler and the array of perforated elements 5 for the outlet ofthe gas once treated, one or more walls for the separation of the space,and in particular for the separation of the portions 11 and 12 of thecontainer, so that the gas emissions can go up inside the container 1only through the holes in the flanges and so that the absorbing solutionis prevented from going upwards.

Thanks to the special internal structure of the device of the invention,and in particular to the separation walls described above, the gasbubbles are subjected to a treatment by passing through the absorbingsolution in the lower part of the container, then they go upwardsthrough the cells formed by the separation walls up to the outlet in theupper part of the container; this occurs with a particular ease for thegas bubbles to go upwards, carried and directed to the outlet, andwithout risk for the absorbing solution to spill outside, thanks to thestabilization given also to it by the presence of the separation walls.

The device of the invention can be produced with different shapes andsize from those illustrated in the attached figures, depending on theflue on which the device is to be installed. The present device can befurthermore installed also in industrial plants and may be useful in theshipbuilding industry for installation on the exhaust systems of largeships, and it is an efficient system for abatement of the noxiousemissions also in these cases, with important benefits for theenvironment and the people's health.

According to a preferred embodiment of the present device, it furthercomprises sensor means suitable for detecting the level and/or thesaturation degree of the absorbing solution inside the gas bubbler andfor signalling these data to an electronic control unit connected to afault signalling system thereof visible from the outside of the device.Thanks to these sensor means, a user may be informed in real time whenthe solution and/or the external filter require a maintenance service.Further sensor means can be included in the present device for thedetection of the saturation degree of the filter in the collecting tankof the outlet gases and/or of the filter for the regeneration of theabsorbing solution. Also in this case the detected data may besignalled, by means of a dedicated electronic system, on a displayoutside of the container.

The present device may moreover comprise sensor means for measuring thetemperature inside the container, by means of a probe installed that isable to detect the temperature inside the container.

In experiments it was observed that the device of this invention has ahigh efficiency in the abatement of harmful substances, and inparticular of the particulate matters, without requiring for exampleincreased temperature but working under normal pressure and temperatureconditions. The present device does not have therefore any influence onthe operation of the boiler or of the stove to which it is connected, ora negative effect on their consumption. Apart from the abatement of theparticulate matters, the present absorbing solution is also capable ofcapturing up to 50% of the CO₂ emitted by the discharges of stoves,boilers and commercial ovens. As described in more detail below, it wasexperimentally observed a significant reduction of particulates in theemissions for the same vehicle on which the opacity of the exhaust ismeasured before and after the installation of the device of theinvention.

The present device is also useful for reducing noxious substances inemissions from stoves and boilers that use any fuels, including wood,pellet, gas, fuel oil.

A first main advantage of the present device and of the method of theinvention is represented by the fact that the absorbing solution usedcan be an aqueous solution and in general the solutes of possible use,in particular ethylene glycol, are non-polluting products, completelyinnocuous for the environment. The present device, therefore, not onlyallows efficiently reducing the emission of pollutants in theatmosphere, but it does not introduce other pollutants in theenvironment.

Still a further advantage of the present device and method isrepresented by the fact that the absorbing solution can be continuouslyregenerated inside the plant where the device is installed, in a simpleand environmentally friendly way, also giving the possibility to collectthe residues of particulate accumulated in an external filter, which maybe easily replaced once exhausted.

The present invention has been described up to here with reference topreferred embodiments. It should be understood that there may be otherembodiments deriving from the same inventive core, as defined by thescope of protection of the claims given hereinafter.

1. A device for the abatement of noxious emissions in exhaust gases fromdomestic heating plants and/or from wood-burning ovens for domestic andcommercial use, comprising: a tight container of substantiallycylindrical shape, provided with a duct (E) for the inlet of exhaustgases to be treated and a duct (U) for the outlet of exhaust gasestreated, inside of which container are positioned at least two portionssubstantially cylindrical, coaxial to said container, having surface,and joined together by a flange with holes, on said surfaces and beingrespectively positioned in a radial pattern two arrays of perforatedelements and that put in communication the inner portions havingsurfaces and with an interspace formed between said surfaces and theinner surface of said container so that the exhaust gases to be treatedenter inside said container through said perforated elements in a lowerpart of the container, go upwards in said interspace through said holesof the flange and exit through said perforated elements in an upper partof the container, said device further comprising an absorbing solutionin such amount as to maintain said perforated elements completelyimmersed in said solution, and one or more separation walls in anintermediate part of the container between said arrays of perforatedelements and so as to prevent a direct fluid communication between saidarrays.
 2. The device according to claim 1, wherein said absorbingsolution is a concentrated aqueous solution of ethylene glycol.
 3. Thedevice according to claim 1, wherein said absorbing solution in saidcontainer is in such amount that said array of elements is completelyimmersed in said solution, whose level exceeds the height of saidelements of 5-10 cm.
 4. The device according to claim 1, furthercomprising sensor means for detecting and signalling the level of saidabsorbing solution and/or of its saturation degree.
 5. The deviceaccording to claim 1, wherein said perforated elements and/or have holesplaced only on a surface facing said interspace in container.
 6. Thedevice according to claim 1, wherein said perforated elements areprovided with holes having a diameter ranging between 0.7-5.0 mm.
 7. Thedevice according to claim 1, further comprising a module comprisingmeans for producing electric energy starting from the gas flow powerexiting from a portion of said container in between said array ofperforated elements and said array of perforated elements.
 8. The deviceaccording to claim 1, further comprising a tank external to saidcontainer and downstream of said outlet of the gas treated, said tankbeing provided with a filter able to capture any unburned particlespossibly remained after treatment.
 9. The device according to claim 1,further comprising a tank external to said container and downstream ofsaid outlet of the gas treated, said tank being provided with a filterfor collecting condensate able to collect the absorbing solutionpossibly dragged by the treated gas, and pipes able to bring back thecondensed liquid inside said container.
 10. The device according toclaim 1, further comprising a system for cooling and regenerating saidabsorbing solution by passing said solution through cooling means andthrough a filter able to retain the particulate accumulated in saidsolution, followed by re-introducing the cooled and filtered solutioninside said container.
 11. A method for the abatement of noxiousemissions in exhaust gases from domestic heating plants and/or fromwood-burning ovens for domestic and commercial use, comprising treatingsaid exhaust gases coming from said plants and/or ovens before theirdischarge in atmosphere by bubbling said gases through an absorbingsolution in a device as defined in claim
 1. 12. The method according toclaim 11, wherein said gases to be bubbled through said solution are infinely divided form.